The ancient skull was found in two pieces (Image: AP/Stone Age Institute, Sileshi Semaw, HO)

Fossil hunters in Ethiopia have unearthed an ancient skull which they say could be a "missing link" between Homo erectus and modern people.

The cranium was found in two pieces and is believed by its discoverers to be between 500,000 and 250,000 years old.

The project's director, Dr Sileshi Semaw, said the fossilised specimen came from "a very significant time" in human evolutionary history.

It was found at Gawis in Ethiopia's north-eastern Afar region.

Stone tools and fossilised animals including two types of pigs, zebras, elephants, antelopes, cats, and rodents were also found at the site.

The skull appeared "to be intermediate between the earlier Homo erectus and the later Homo sapiens," Sileshi Semaw, an Ethiopian research scientist at the Stone Age Institute at Indiana University, US, told a news conference in Addis Ababa.

'Wealth of information'

The palaeoanthropologist said most fossil hominids were found in pieces, but the near-complete skull provided a wealth of information.

"[It] opens a window into an intriguing and important period in the development of modern humans," he explained.

Little is known about the period during which African Homo erectus supposedly evolved into our own species Homo sapiens.

The fossil record from Africa for this period was sparse and most of the specimens poorly dated, project archaeologists said.

The face and cranium of the fossil are recognisably different from those of modern humans, but the specimen bears unmistakable anatomical evidence that it belongs to the modern human ancestral line, Dr Semaw said.

Scientists conducting surveys in the Gawis River drainage basin found the skull in a small gully.

Over the last 50 years, Ethiopia has been a key site for archaeologists hunting for fossil human ancestors.

Gawis is situated near Hadar, where palaeoanthropologist Donald Johanson found the 3.2-million-year-old remains of "Lucy", the partial skeleton of a hominid belonging to the species Australopithecus afarensis, in 1974.